Process of making cadmized bearings



April 8, R E; QUENEAU ETAL 2,237,314

PROCESS OF MAKING CADMIZED BEARINGS Filed May 27, 1958 PENETRA T/O/VINVENTORS PauZE ueweau fller' M/faZZ.

ATTORNEY or anti-gelling properties.

Patented Apr. 8, 194-1 2,237,314 PROCESS OF MAKING CADMIZED BEARINGSPaul Etienne Queneau, Copper Cliff, Ontario, Canada, and Albert MangoldHall, Huntington, W. Va., assignors to The International Nickel Company,Inc., New York, N. Y., a corporation of Delaware Application May 21,1938, Seriai no. 210,371

(Cl. ill-70.1)

8 Claims.

'I'hepresent invention relates to anti-friction bearings and to a methodof making the same,

and, more particularly, to anti-friction bearings made of a body ofcorrosion-resistant metal surface impregnated with cadmium which impartsor substantially improves the anti-friction or anti-gelling propertiesof the metal, and to a method of impregnating the surface of the bodywith cadmium from the vapor state.

In many types of apparatus, equipment and machinery, bearings arerequired which must have high mechanical strength and/or greatresistance to corrosion coupled with anti-friction No available metal oralloy, so far as we are aware, has this desirable combination ofproperties, but wehave discovered that satisfactory bearings may be madeof a metallic body having the desired physical properties and/or thenecessary resistance to corrosion but deficient anti-friction oranti-galling properties by impregnating the surface with cadmium whichimpartsor substantially improves the anti-friction or anti-gellingproperties of the metallic body from the vapor state.

It is an object of the present invention to provide an improvedanti-galling and anti-friction structure constituted of a metal or alloyso treated as to fulfill the multiple requirements of strength,hardness, resistance to heat and corrosion, and ability to operate underconditions of sliding and/or rolling friction without failure throughgalling or seizing.

It is another object of the invention to provide a process of makingbearings comprising impregnating a body of metal or alloy possessingsatisfactory strength, hardness and/or resistance to corrosion, butbeing deficient in anti-friction or anti-galllng properties, withcadmium from the vapor state whereby satisfactory anti-gallingproperties are imparted to the body.

It is a further object of the present invention to provide a process ofimpregnating metals and alloys with cadmium to improve the resistance ofthe metals and alloys to the attack of corrosive agents,

It is also within the contemplation of the invention to provide aprocess of impregnating metals and alloys with cadmium from the vaporphase. in which an alloy is formed between the base metal or alloy andthe cadmium.

Other objects and advantages of the invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawing, in which:

Fig. 1 is a somewhat diagrammatic sectional elevational view of anapparatus for carrying out the process of the present invention;

Fig. 2 depicts a photomicrograph of a copper body impregnated withcadmium by the process embodying the present invention; and

Fig. 3 depicts graphically the penetration of cadmium intorepresentative base metals and alloys impregnated by the process of thepresent invention, as determined by spectrographic analyses.

Broadly stated the invention contemplates a bearing comprising a body orbase of suitable metal or alloy such as copper; nickel, coppernickelalloys, brass, steel, stainless steel, etc., impregnated at the surfacewith cadmium from the vapor state. The invention also contemplates aprocess of impregnating-the surface of the base metal or alloy withcadmium. under such conditions that the cadmium penetrates into the baseto which it imparts anti-friction and anti-galling properties.

As those skilled in the art will readily understand, the selection ofthe base metal or alloy will be governed by the requirements of theparticular application. For example, if high tensile strength is desiredcombined-with lightness (low specific gravity), an aluminumalloy of theage hardening type is preferably selected, but if hardness, highstrength and corrosion resistance are desired, an alloy of the stainlesstype, such as nickel-copper alloy, stainless steel and the like ispreferably selected.

Generally speaking, the process embodying the present inventioncomprises preparing the surface of the metal or alloy to be impregnatedto receive or imbibe cadmium from the vapor state, exposing the metal orarticle under properly correlated conditions of temperature and time tocadmium vapor in an atmosphere that is neutral or reducing with respectto the surface to be impregnated until the desired impregnation hastaken place, and then cooling the impregnated article. Under certaincircumstances, it may be desirable to heat treat the impregnated articleto improve the properties of the impregnated surface and/ormodify theproperties of the alloy of the base metal and the cadmium and/or controlthe depth of the case, i. e., the depth of the cadmium penetration, etc.This heat treatment may be performed in the cadmizing chamber or theimpregnated pieces may be removed therefrom and heat treated in anysuitable apparatu's.

The nature of the preparation of the surface to receive or imbibe thecadmium will vary demium vapor.

pending on the metal or alloy to be impregnated. In general, the metalsand alloys may be divided into two broad classes, viz., those which maybe directly impregnated upon exposure thereof to cadmium vapors in aneutral or reducing atmosphere while in the solid state and at atemperature not in excess of the boiling point of cadmium, and thosewhich may not be directly impregnated under these conditions.

In the case of metals and alloys which can be directly impregnated withcadmium under the aforesaid conditions, the preparation of the surfaceto be impregnated preferably comprises the removal of dirt, grease, etc.by any suitable means, for example by grinding, blasting, and the like,followed by a thorough pickling to remove any oxygen-containing materialor other passive film that may have formed on the surface.Representative examples of such metals and alloys which have beensuccessively cadmized by the process embodying the present invention arenickel, copper, nickel-copper alloys, brass, bronze and nickel-chromium-iron alloys. These metals and alloys are characterized bytheir ability to alloy with cadmium.

In the case of metals and alloys which may not be directly impregnatedwith cadmium under the aforementioned conditions, the preparation of thesurface to be impregnated preferably comprises cleaning and pickling inthe manner already described, af-ter which an intermediate layer of abonding metal or alloy is deposited, for example by electroplating,spraying etc., upon the base metal. The bonding metal or alloy should beone which bonds well or alloys with the base metal when heated therewithafter deposition and one which may be directly impregnated with cadmiumfrom the vapor state under the conditions described hereinbefore.Representative examples 'of metals and alloys which have beensuccessfully cadmized in accordance with the present invention afterpreparing the surfaces in this manner are aluminum plated with nickel orcopper and steel plated with nickel. Aluminum and iron do not alloyreadily with cadmium.

The cadmizing proper may be performed in any suitable gas filledcontainer into which cad-' mium vapors may be introduced. An apparatusthat has proved satisfactory in service is illustrated in Fig. 1, inwhich reference numeral I represents. a cadmizing chamber comprising abottom wall 2, sidewalls 3.and a removable cover I. Within chamber I isa carbon pot 5 for holding and vaporizing the molten cadmium. A gasket 6placed between the top 4 and walls 3 assures a gas-tight cadmizingchamber. A supply tube 1 communicates with the interior of the chamber Iand connects it with a suitable sourceof gas to provide a neutral orreducing atmosphere within, the cadmizing chamber I. Air may be removedby flushing chamber I with neutral or reducing gas supplied throughtube 1. An exhaust tube 8 is provided to carry off the air and gases.After the chamber I has been flushed to remove the air, thenon-oxidizing atmosphere may be retained by maintaining neutral orreducing gas under pressure in chamber I, or the non-oxidizing gas maybe circulated through the chamber using a suitable filter to preventoutflow of cad- It has been found advantageous to cover the moltencadmium in the pot with a blanket of powdered charcoal and ammoniumchloride to assist in maintaining a reducing atmosphere and inpreventing formation of passive areas on the article being cadmized. 5The blanket charcoal.

serves also to protect the cadmium against oxidation when the cover 6 isremoved.

Any suitable gas may be used to provide the neutral or reducingatmosphere. Satisfactory results have been obtained-using carbonmonoxide and pure dry hydrogen.

The pieces of metal or alloy to be impregnated may be supported in thechamber I in any desired manner. Rod shaped articles I0, for example,may be supported on brackets 9 as illustrated in Fig. 1. The articles tobe impregnated are maintained at a temperature not in excess of theboiling point of cadmium and preferably within the range of about 900 toabout 1200 F. during the cadmizing treatment. In the apparatusillustrated in Fig. 1 the chamber I, the pieces to be impregnated andthe carbon pot maybe heated from an external source of heat, for exampleby placing the apparatus in a mufiie furnace. Any other suitable sourceof heat may be provided, as those skilled in the art will readilyunderstand. I It has been found that at a temperature of about 900 F. toabout 1200 F. suflicient cadmium vapor is produced to yield satisfactorydeposits. The time of exposure to cadmium vapors will depend upon thetemperature, the thickness and structure of the case. desired, etc.Satisfactory results have been obtained under the conditions mentionedhereinbefore in as short a time as about 30 minutes. No practicaladvantage appears to result from exposures longer than about 10 hours,and in most cases about 3 hours represents a practical maximum. It isnot essential in 'all cases that the articles to be impregnated bepreheated, as good penetration of cadmium may be obtained in someinstances by passing hot cadmium vapors over unheated articles undersuit- Example N01 1 A copper bar was cleaned by grinding and thenpickled in dilute nitric acid. Thereafter it was placed in a. cadmizingchamber filled with pure dry hydrogen and exposed to cadmium vapors forabout one hour at a temperature of about 1000 F. The cadmium bath wascovered with powdered The impregnated bar had a silver white, unspangledand finely crystalline case, the cadmium having penetrated about 0.001inch (microscopic measurement) uniformly into the surface. I

Similar results were obtained when the temperature was about 900 F. andthe time about 1.5 hours.

Fig. 2 represents a photomicrograph of the structure of a cross-sectionof the first mentioned test piece at a magnification of .500 diameters.

Example No. 2

A nickel bar was cleaned by rinsing in carbon tetrachloride and thenpickled in dilute aqueous nitric acid. Thereafter it was exposed tocadmium vapor for about 3 hours at a temperature It will be observedthat three distinctfinely crystalline and metallic gray in color.

Example No. 3

' A bar of nickel-copper alloy containing approximately 67% Ni, Cu, 2%Fe and 1% Mn was pickled in dilute nitric acid. The cadmizing chamberwas filled with pure dry hydrogen and the cadmium covered with' amixture of powdered charcoal and ammonium chloride. The bar wasmaintained at about 1100 F. for about 10 hours in contact with cadmiumvapor.- A-uniform penetration to a depth of' about 0.010 to 0.020"(microscopic measurement) had occurred on the surface of the bar.

Abar about 1" x 1" x '7" of nickel-copper alloy containing about 67% Ni,30% Cu and 3.25% A1,,v treated under similar conditions for about 30minutes at about 1100 F., was found to have a very even case of large,bright silver white spangles. A similar bar of the same alloy whentreated at about 1000 F. for about 30 minutes had a smooth case on thetop surface; a coarser and somewhat spangled case on the under surfacewhile the side surface showed a gradation in structure from that of thebottom to that of the top. Thecase was bright and free from oxidation. Athird'specimen of about the same size was treated at about 900 F. foraboutminutes. A very smooth and even surface impreg-. nation occurred onall sides, the texture of the surface being finely granular.

It will be seen from the foregoing that the structure of the case can bemodified by varying the temperature and the time of cadmizing. Ingeneral it may be said that the structure of the case becomes morecoarsely crystalline and tends to become more spangled with increasingtemperature.

A bar of yellow brass containing about 67% Cu and about 33% Zn afterbeing cleaned by grinding and pickled in dilute nitric acid was cadmizedat about 1000" F. foraboiit 1.5 hours under conditions similar toExample No. 2. The surface Example N0. 4

had much the same appearance as that applied Example N0. 5

A bar of nickel-chromium-lron alloy contain- 5 ing about Ni, about 13%Cr and about 7% Fe was cleaned by grinding and pickled in warmnitric-hydrofluoric acids solution. It was then exposed to cadmium vaporfor about 7 hours at a temperature of about 900 F. in an atmosphere ofdry hydrogen. The case was smooth, unspangled, It has been found inpractice that alloys of this type maybe successfully impregnated atabout 900 F. in about 3 to '7 hours.

Example No. 6

A bar of plain carbon steel or the s. A; E. 1020 type containingabout0.20% C was subjected to surface grinding and then dipped in carbontetrachloride to remove any grease or the like.

Thereafter it was electrolytically cleaned in trisodium phosphate. Thecleaned bar was then placed in a nickel plating bath containing thefollowing ingredients:

. Oz. per gal. NiSO4.7H2O About 28.5 NiCL2.6H2O About" 6.0 I-bBO-.;About 4.0

The bath was maintained at a temperature of about to F. and at a pHvalue of about 5.3 to 5.5. A cathode current density of about 15 to 20amperes persq. foot was employed to deposit a layer of nickel on thesteel bar. The nickel plated bar was then exposed to cadmium vapors inan atmosphere of dry hydrogen at a temperature of about 1150 F. forabout 2 hours. The case was of the smooth, non-Spangled, finelycrystalline type.

Similar results were obtained when aluminum was carefully treated toremove all dirt and oxide test piece and then polishing off a definitelayer before sparking again.

The results of these determinations are shown graphically in Fig. 3 forthe following specimens Copper cadmized for 1 hour at 1000 F curve AYellow brass cadmized for 1.5 hours at 1000 F curveB Nickel cadmized for3 hours at 1200 F curve C NiCrFe cadmized for 7 hours at 900 F curve DThe concentration values, plotted on the ordinate axis, were obtained byassuming the cadmium concentration on the surface of the cadmizedspecimen to be unity.

The microscopic and spectrographic studies ap- A parently demonstratethat in impregnating those metals and alloys which a e directly cadmizedby the process embodying the present invention, the cadmium penetratesinto and forms an alloy with the base metal. This is clearly portrayedin Fig. 2 for cadmized copper, in which distinct outer, intermediate andinner strata may be seen. The intermediate stratum is believed to be acadmiumcopper intermetallic compound since the concentration-penetrationcurve A in this zone shows a horizontal portion indicating substantiallyconstant cadmium content for a measurable depth. A similar stratum wasobserved under the microscope on polished sections of cadmized brass butit was less regular and thinner than in the case of copper whichprobably accounts for the absence of a similar horizontal portion incurve B of Fig. 3. In the cadmium impregnated nickel andnickel-chromium-iron alloy. the cadmium appears to form a solid solutiontype of alloy with the base metal. In all four curves, however, it is tobe observed that the cadmium concentration decreases rapidly'to zerofrom a maximum at the surface of the case inwardly. indicating thatthere is practically no pure cadmium on the surface of the cadmizedarticles but, on the contrary, that the impregnated case is essentiallya solid solutionpr alloy of the cadmium in the basemetal or alloy, thecadmium decreasing somewhat asymptotically from a maximum at the surfaceof the case to zero.

In those metals which cannot be directly cad- I alloy bond between thebase metal and the antigalling surface.

The anti-friction and anti-galling properties of the cadmized bearingsof the present invention are very satisfactory] Metals and alloys whichper se have very poor bearing properties but which would otherwise bedesirable for bearings due to other valuable properties, e. g.,strength,

hardness, resistance to corrosion, etc., may be made into excellentbearings by the cadmizing process of the present invention. For.example,

' when a piece of nickel-copper alloy about t2" x x 2" and containingabout 67 Ni, 30 Cu and 3.25 Al was placed in a friction testing machineso that it reciprocated along another piece of the same metal about 36times per minute under a load of about 1500 pounds, 'galling wasproduced in about 20 to 50 seconds whereas when one of the surfaces wascadmized no galling occurred after 3 hours, although some wear could bedetected. In these tests the bearing surfaces were lubricated withcastor oil.

10 hours to impregnate the surface of the metal with cadmium bydiffusion forming an integral and inseparable case and impartinganti-friction and anti-galling properties thereto, and removing saidmetal from contact with cadmium vapor when said case reaches apredetermined depth and possesses a cadmium concentration decreasingimmediately from the surface of the case rapidly andsomewhatasymptotically to zero, and while said case at its surface issubstantially devoid of a cadmium layer of appreciable thickness.

'2. A process of making bearings comprising exposing a metal alloyablewith cadmium to anti-friction and anti-galling properties thereto,

Cadmized bearings of the present invention, in

addition to vastly improved anti-friction properties, exhibit increasedresistance to corrosion due to the protective action of the cadmium.This is of particular importance inthose cases where the base metal useddoes not possess sufdcient chemical stability to resist the corrosiveagents to which it is exposed. Iron and low alloy steels, for exampleare readily corroded in damp atmospheres,

but whenimpregnatedwith cadmium they resist rusting and corrosion forlong periods of time.

In the specification and claims the term base metal" is used todesignatemetals or alloys of the types mentioned hereinbefore, i. e.,iron, steel and their. alloys; nickel and its alloys; copper, brass,bronze and other copper alloys; aluminum and its various alloys; etc.

Although the present invention has been described in connection withcertain preferred embodiments, modifications and varations may beresorted to, as those skilled in the art will readily understand. Thus,the method of impregnating base metals with cadmium from the vaporphase, as described hereinbefore, may be utilized for purposes otherthan producing bearings, for example, to rendermetals and alloys such asiron and steel resistant to rusting and corrosive attack. Such andremoving said metal from contact with cadmium vapor when said casereaches a predetermined depth and possesses a cadmium concentrationdecreasing immediately from the surface of the case rapidly and somewhatasymptotically to zero, and while said case at its surface issubstantially devoid of a cadmium layer of appreciable thickness.

3. A process of making bearings as set forth in claim 2 in which themetal alloyable. with cadmium is nickel.

4. A process of making bearings as set forth in claim 2 in which themetal alloyable with cadmium is cuprous metal, and the time of exposureis maintained between about 30 minutes and 3 hours.

5. A method of making bearings comprising cleaning thegsurface of a bodyof base metal that does not alloy readily with cadmium, depositing onthe surface of said body a layer of metal alloyable with the base metaland with cadmium to form a coated body, exposing the coated body tocadmium vapor under nonoxidizing conditions at a temperature within therange of about 900 F. to 1200 F. for a period of time not exceedingabout 3 hours to impregnate the surface of the coated body. with cadmiumby diffusion forming an integral and inseparable surface case andimparting antifriction and anti-galling properties thereto, and

' removing said body from contact with cadmium steel and the layer metalis nickel.

' 'l. A process .of surface treating metals with cadmium comprisingexposing a metal alloyable with cadmium to cadmium vapor, said metalbeing maintained at a temperature between 900 F. and the boiling pointof cadmium and under non-oxidizing conditions for a period of time notexceeding about 10 hours to impregnate the surface of the metal withcadmium by diffusion forming an integral and inseparable case, andremoving said metal from contact with cadmium vapor when said casereaches a pre- Y of appreciable thickness.

V 2,237,314- r 5' determined depth and possesses a cadmium 8. A processof making bearings as set forth concentration decreasing immediatelyfrom the in claim 2. in which the metal alloyable with surface of thecase rapidly and somewhat asymp- 'cadmium is a nickel alloy.

totically to zero, and while said case at its surface is substantiallydevoid of a cadmium layer 5 PAUL ETIENNE QUENEAU.

ALBERT MANGOLD HAIL.

CERTIFICATE OF CORRECTION.

April 8, 19in.

Patent No. 2,257,31h.

' PAUL ETIENNE QUENEAU, ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent. requiring correction as follows: Page 1,first column, line 29, after the word "deficient" insert --in--; line2b., strike out "from the vapor state" and insert the same after the syiilabl'e "mium" in line 22; page 3 first column, line 1414., after"case'insert --produced by impregnating the surface ofthe base metal withcadmium-; line 71, for

"case" read --surface-- and that the said Letters Patent should be readwith this correction therein'that the same may conform to the record :ofthe case in the Patent Office,

Signed and sealed this 20th day of May, A. D. I 19in.

fienry Van Arsdale,

(seal) Acting Commissioner of Patents.

